Method for deodorizing polyolefin granulates

Abstract

A gaseous mixture of steam and air, a gaseous mixture of steam and nitrogen, or pure steam are passed around polyolefin granules in a deodorizing apparatus. The result is that the polyolefin granules have markedly improved properties with respect to odor and taste, and these are retained in moldings produced from the granules.

We claim:  
     
       1. A process to deodorize polyolefin granules,which contain no units derived from dienes, in an apparatus, which comprises firstly passing a gaseous mixture of steam and air, a gaseous mixture of steam and nitrogen, or pure steam around the polyolefin granules at from 80 to 150° C., where the amount of steam used is from 0.3 to 2 kg of steam per kg of polyolefin granules, and then returning some or all of the steam, the steam/air mixture or the steam/nitrogen mixture to the apparatus after it has passed through the apparatus. 
     
     
       2. The process of claim  1 , wherein the duration of treatment is from 2 minutes to 48 hours. 
     
     
       3. The process of claim  1 , wherein the temperature is from 90 to 130° C. 
     
     
       4. The process of claim  1 , wherein the polyolefin granulates comprises polyolefin which is selected from the class encompassing polyethylene, polypropylene, poly-1-butene, polyisobutene, poly-4-methyl-1-pentene, copolymers of ethylene and propylene, terpolymers of ethylene, propylene and other hydrocarbons, mixtures of polypropylene, rubber and polyethylene and mixtures of the constituents mentioned above. 
     
     
       5. The process of claim  1 , wherein the polyolefin granulates comprise polypropylene having an MFI (230/5) of from 0.4 dg/min to 2 dg/min and from 0 to 11% by weight of polyethylene. 
     
     
       6. A process to coat or to produce shaped objects, wherein the material used is polyolefin granulates treated according to the process of claim  1 . 
     
     
       7. A process to coat or to produce shaped objects for the domestic goods sector and for the construction of equipment, wherein the material used is polyolefin granulates treated according to the process of claim  1 . 
     
     
       8. A process to coat or to produce containers or piping, wherein the material used is polyolefin granules treated according to the process of claim  1 . 
     
     
       9. The process of claim  2 , wherein the duration of treatment is from 1 to 10 hours. 
     
     
       10. The process of claim  1 , wherein the polyolefin granules are polyethylene or polypropylene.